Surprising how much open talk there is about swapping PCMs and Speedos. It is a Federal offense if you sell your car without disclosing any mileage tampering. You can do anything you want to the vehicle while you own it. Heck turn the mileage back to zero if you like, but you must tell the buyer.
I am not going to release all the info. The PCM does track your mileage. The PCM checks for VSS signal (Vechicle Speed Sensor). This is a PPM (Pulses Per Mile). If the signal is lost, you will get a check engine light.
If you disconnect the signal at speedometer (no check engine light will be triggered), you will still be logging miles via the PCM. If you swap out your PCM, the VIN number of the Vehicle will not match your PCM entry. If you buy a PCM on Ebay, it will show the VIN of the vehicle it was pulled from.
These are all things to check prior to buying a used Viper.
I recently checked a Viper that appeared to have 4x more miles than indicated…. I was correct, the VIN on the PCM did not match. Bingo!
Let your gut instinct alert you. If the car looks like it has a lot more miles on it…it might. Look at the paint, the condition of the seats, the date code on the tires, etc. Run a car fax and have a local Dodge dealer run a report. Vipers are a sizeable investment. Don’t get emotionally involved with a purchase. Many Vipers that I inspect become a “Do not buy” recommendation.